Alkylation of aromatic hydrocarbons



Feb. 14, 1961 H. s. BLOCH 2,971,992

ALKYLATION 0F AROMATIC HYDROCARBONS Filed Dec. 30, 1957 Bottoms awn 0gauaumg Van! IN VE/V TOR.-

Herman .S. Bloch BY.- N n KMLZIZLM Off Gas Rena/0r Benzene ATTORNEYS.

United States Patent ALKYLATION OF AROMATIC HYDROCARBONS Herman S.Bloch, Skokie, 111., assignor, by mesne assignments, to Universal OiiProducts Company, Des Plaines, 111., a corporation of Delaware FiledDec. 39, 1957, Ser. No. 705,860

7 Claims. (Cl. 260-671) This invention relates to a process for thealkylation of an aromatic hyrocarbon, and more particularly relates to aprocess for the alkylation of an alkylatable benzene hydrocarbon with anolefin-acting compound, and still more particularly relates to thealkylation of benzene with ethylene and propylene in combination withunreactive gases. Further, this invention relates to a combinationprocess including the steps of alkylation, gas-liquid separation,fractionation, countercurrcnt gas-liquid absorption, and selectiverecycle to obtain alkyl transfer.

An object of this invention is to produce alkyl-aromatic hydrocarbons,and more particularly to produce alkylated benzene hydrocarbons. Aspecific object of this invention is to produce ethylbenzene, a desiredchemical intermediate, which ethylbenzene is utilized in largequantities in dehydrogenation processes for the manufacture of styrene,one starting material for the production of some synthetic rubbers.Another specific object of this invention is to produce alkylatedaromatic hydrocarbons within the gasoline boiling range having a highantiknock value and which may be used as such or as a component ofgasoline suitable for use in automobile and airplane engines. A furtherspecific object is a process for the production of cumene by thereaction of benzene with propylene, which cumene product is oxidized inlarge quantities to form cumene hydroperoxide which is readilydecomposed into phenol and acetone. Another object of this invention isa process for the production of para-diisopropylbenzene whichdiisopropylbenzene is oxidized to terephthalic acid, one startingmaterial for the production of some synthetic fibers. Still anotherobject of this invention is to provide a process for the introduction ofalkyl groups into aromatic hydrocarbons of high vapor pressure at normalconditions with minimum loss of said high vapor pressure aromatichydrocarbons and maximum utilization thereof in the process. The furtherobject of maximum boron trifiuoride recovery for reuse as a catalyst inthis process, along with other objects of this invention, Will be setforth hereinafter as part of the accompanying specification.

In prior art processes for the alkylation of aromatic hydrocarbons witholefin hydrocarbons, it has been disclosed that it is preferable toutilize molar excesses of aromatic hydrocarbons. In such processes it isgenerally preferable to utilize greater than two mols of aromatichydrocarbon per mol of olefin hydrocarbon, and in many cases, for bestreaction, it is preferred to use three or more mols of aromatichydrocarbon per mol of olefin hydrocarbon. This has been found necessaryto prevent polymerization of the olefin hydrocarbon from taking placeprior to the reaction of the olefin hydrocarbon with the aromatichydrocarbon. While generally satisfactory proc esses have resulted fromthe utilization of such molar excesses of aromatic hydrocarbons in thepresence of solid or liquid catalysts of the class known asFriedel-Crafts metal halides, a problem arises when these molar excessesare utilized in connection with the alkylation of aromatic hydrocarbonsof high vapor pressure at normal conditions,

particularly when the olefin hydrocarbon utilized as the olefin-actingcompound or alkylating agent is a normally gaseous olefin hydrocarbonsuch as ethylene, propylene, l-butene, Z-butene, or isobutylene, and theproblem is further accentuated when this alkylation is carried out inthe presence of a gaseous acidic catalyst such as exemplified by borontrifluoride. The above mentioned olefin hydrocarbons are often presentas minor quantities in various refinery gas streams containing majorquantities of other gases such as hydrogen, nitrogen, hydrogen sulfide,and hydrocarbons such as methane, ethane, propane, n-butane, andisobutane. It has been suggested in the prior art that the aromatichydrocarbon to be alkylated can be utilized in a gas-liquid absorptionzone for the absorption of the olefin hydrocarbon from such gas streams.When the aromatic hydrocarbon thus utilized has a high vapor pressure atnormal conditions, concurrent loss of the aromatic hydrocarbon isobserved due to the vapor pressure which the aromatic hydrocarbon exertsin the absorption zone, which aromatic hydrocarbon is then carried fromthe absorption zone along with the unreactive gases which the prior artsuggests can be vented from the absorption zone. Furthermore, such aprocess is dependent upon the solubility coefficient of the olefinhydrocarbon in the aromatic hydrocarbon in the absorption zone at theconditions of temperature and pressure utilized therein. It is obviousthat at best such a process is inefiicient. By means of the process ofthe present invention, these and other disadvantages in the hereinabovedescribed processes can be overcome.

in one embodiment the present invention relates to a process for theproduction of an alkylated aromatic hydrocarbon which comprises passingto a reaction zone an alkylatable aromatic hydrocarbon, an unsaturatedorganic compound, and recycle polyalkylaromatic hydrocarbon absorber oilproduced as hereinafter described and containing boron trifiuoride,reacting therein said alkylatable aromatic hydrocarbon with saidunsaturated organic compound at alkylation conditions in the presence ofboron trifluoride as the alkylation catalyst, passing efiiuentcomprising boron trifiuoride, alkylatable aromatic hydrocarbon,alkylated aromatic hydrocarbon and polyalkylated aromatic hydrocarbonfrom said reaction zone to a gasliquid separation zone, separating gasfrom liquid in said separation zone, passing said gas to a lower regionof a gas-liquid absorption zone hereinafter described, passing liquidfrom said separation zone to a fractionation zone, fractionating saidliquid in said zone to separate overhead unreacted alkylatable aromatichydrocarbon, recycling said unreacted alkylatable aromatic hydrocarbonto the reaction zone, passing alkylated aromatic hydrocarbon to a secondfractionation zone, fractionating said alkylated aromatic hydrocarbon insaid second fractionation zone to separate overhead desired alkylatedaromatic hydrocarbon product, removing said product from the process,passing polyalkyiated aromatic hydrocarbon from said secondfractionation zone to an upper region of a gas-liquid absorption zone asabsorber oil therefor, countercurrently contacting saidpolyalkylaromatic hydrocarbon with the hereinabove described gas feed tosaid zone, venting from the process non-absorbed gas from said zone, andpassing said absorber oil containing boron trifiuoride from said zone tothe reaction zone as aforesaid.

In another embodiment the present invention relates to a process for theproduction of an alkylated aromatic hydrocarbon which comprises passingto a reaction zone an alkylatable aromatic hydrocarbon, an olefin, andre cycle polyalkylaromatic hydrocarbon absorber oil produced ashereinafter described and containing boron trifiuoride, reacting thereinsaid alkylatable aromatic hydrocarbon with said olefin at alkylationconditions in the presence of boron trifiuoride as the alkylationcatalyst, passing efi'luent comprising boron trifluoride, alkylatablearomatic hydrocarbon, alkylated aromatic hydrocarbon and polyalkylatedaromatic hydrocarbon from said reaction zone to a gas-liquid separationzone, separating gas from liquid in said separation zone, passing saidgas to a lower region of a gas-liquid absorption zone hereinafterdescribed, passing liquid from said separation zone to a fractionationzone, fractionating said liquid in said zone to separate overheadunreacted alkylatable aromatic hydrocarbon, recycling said unreactedalkylatable aromatic hydrocarbon to the reaction zone, passing alkylatedaromatic hydrocarbon to a second fractionation zone, fractionating saidalkylated aromatic hydrocarbon in said second fractionation zone toseparate overhead desired alkylated aromatic hydrocarbon product,removing said product from the process, passing polyalkylated aromatichydrocarbon from said second fractionation zone to an upper region of agas-liquid absorption zone as absorber oil therefor, countercurrentlycontacting said polyalkylaromatic hydrocarbon with the hereinabovedescribed gas feed to said zone, venting from the process non-absorbedgas from said zone, and passing said absorber oil containing borontrifluoride from said zone to the reaction zone as aforesaid.

In a further embodiment the present invention relates to a process forthe production of an alkylated benzene hydrocarbon which comprisespassing to a reaction zone an alkylatable benzene hydrocarbon, anormally gaseous olefin, and recycle polyalkylbenzene hydrocarbonabsorber oil produced as hereinafter described and containing borontrifluoride, reacting therein said alkylatable benzene hydrocarbon withsaid normally gaseous olefin at alkylation conditions in the presence ofboron trifluoride as the alkylation catalyst, passing efiluentcomprising boron trifluoride, alkylatable benzene hydrocarbon, alkylatedbenzene hydrocarbon, and polyalkylated benzene hydrocarbon from saidreaction zone to a gasliquid separation zone, separating gas from liquidin said separation zone, passing said gas to a lower region of agas-liquid absorption zone hereinafter described, passing liquid fromsaid separation zone to a fractionation zone, fractionating said liquidin said zone to separate overhead unreacted alkylatable benzenehydrocarbon, recycling said unreacted alkylatable benzene hydrocarbon tothe reaction zone, passing alkylated benzene hydrocarbon to a secondfractionation zone, fractionating said alkylated benzene hydrocarbon insaid second fractionation zone to separate overhead desired alkylatedbenzene hydrocarbon product, removing said product from the process,passing polyalkylated benzene hydrocarbon from said second fractionationzone to an upper region of a gasliquid absorption zone as absorber oiltherefor, countercurrently contacting said polyalkylbenzene hydrocarbonwith the hereinabove described gas feed to said zone, venting from theprocess non-absorbed gas from said zone, and passing said absorber oilcontaining boron trifluoride from said zone to the reaction zone asaforesaid.

In a specific embodiment the present invention relates to a combinationprocess for the production of ethylbenzene which comprises passing to areaction zone benzene, ethylene, and recycle diethylbenzene absorber oilproduced as hereinafter described and containing boron trifluoride,reacting therein said benzene with said ethylene at alkylationconditions in the presence of boron trifluoride as the alkylationcatalyst, passing effluent comprising boron trifluoride, benzene,ethylbenzene, and polyethylbenzene from said reaction zone to agas-liquid separation zone, separating gas from liquid in saidseparation zone, passing said gas to a lower region of a gas liquidabsorption zone hereinafter described, passing liquid from saidseparation zone to a fractionation zone,

zene to a second fractionation zone, fractionating said ethylatedbenzene in said second fractionation zone to separate overhead desiredethylbenzene product, removing said ethylbenzene product from theprocess, passing higher boiling polyethylated benzene from said secondfractionation zone to a third fractionation zone, fractionating saidpolyethylated benzene in said third fractionation zone to separateoverhead diethylbenzene, removing higher boiling polyethylatedbenzene'as bottoms from the process, passing said diethylbenzene fromsaid third fractionation zone to an upper region of a gas-liquidabsorption zone as absorber oil therefor, countercurrently contactingsaid diethylbenzene with the hereinabove described gas feed to saidzone, venting from the process non-absorbed gas from said zone, andpassing said absorber oil containing boron trifiuoride from said zone tothe reaction zone as aforesaid.

In another specific embodiment the present invention relates to aprocess for the simultaneous production of ethylbenzene and cumene whichcomprises passing to a reaction zone benzene, ethylene and propylenediluted with unreactive gas, and recycle dialkylbenzene absorber oilproduced as hereinafter described and containing boron trifluoride,reacting therein said benzene with said ethylene and propylene atalkylation conditions in the presence of boron trifluoride as thealkylation catalyst, passing effluent comprising boron trifluoride,unreactive gas, benzene, ethylbenzene, cumene, and polyalkylated benzenefrom said reaction zone to a gas-liquid separation zone, separating gasfrom liquid in said separation zone, passing said gas to a lower regionof a gas-liquid absorp tion zone hereinafter described, passing liquidfrom said separation zone to a fractionation zone, fractionating saidliquid in said zone to separate overhead unreacted benzene, recyclingsaid unreacted benzene to the reaction zone, passing higher boilingalkylated benzene to a second fractionation zone, fractionating saidalkylated benzene in said second fractionation zone to separate overheaddesired ethylbenzene product, removing said ethylbenzene as one productfrom the process, passing higher boiling alkylated benzene from saidsecond fractionation zone to a third fractionation zone, fractionatingsaid higher boiling alkylated benzene in said third fractionation zoneto separate overhead desired cumene product, removing said cumene as thesecond product from the process, passing still higher boilingpolyalkylated benzene from said third fractionation zone to a fourthfractionation zone, fractionating said polyalkylated benzene in saidfourth fractionation zone to separate overhead dialkylated benzene,removing higher boiling polyalkylated benzene as bottoms from theprocess, passing said dialkylated benzene from said fourth fractionationzone fractionating said liquid in said zone to separate overheadunreacted benzene, recycling said unreacted benzene to the reactionzone, passing higher boiling ethylated bento an upper region of agas-liquid absorption zone as absorber oil therefor, countercurrentlycontacting said dialkylbenzene with the hereinabove described gas feedto said zone, venting from the process non-absorbed gas from said zone,and passing said absorber oil containing boron trifluoride from saidzone to the reaction zone as aforesaid.

This invention can be most clearly illustrated with reference to theattached drawing. While of necessity certain limitations must be presentin such a schematic description, no intention is meant to thereby limitthe generally broad scope of this invention. As stated hereinabove, thefirst step of the process of the present invention comprises alkylatingan alkylatable aromatic hydrocarbon with an unsaturated organic compoundat alkylation conditions in the presence of a gaseous acidic catalyst,namely, boron trifluoride, In the drawing, this first step isrepresented as taking place in reaction zone 6. However, the mixture ofalkylatable aromatic hydrocarbon, unsaturated organic compound, andmake-up reaction zone 6 through line 1. The alkylatable aromatichydrocarbon is combined therewith in line 1 by passage through line 2which also provides means for continuous or discontinuous addition ofboron trifiuoride through line 3. Line 4 in the drawing represents meansby which unreacted alkylatable aromatic hydrocarbon is recycled toreaction zone 6. Line 5 in the drawing represents polyalkylaromatichydrocarbon absorber oil containing boron trifluozide which is recycledto the reaction zone.

The unsaturated organic compound, particularly olefinacting compound,and still more particularly olefin hydrocarbon, which may be charged toreaction zone 6 via line 1 may be selected from diverse materialsincluding monoolefins, diolefins, polyolefins, acetylenic hydrocarbons,and also alcohols, ethers, and esters, the latter including alkylhalides, alkyl sulfates, alkyl phosphates, and various esters ofcarboxylic acids. The preferred unsaturated organic compounds areolefinic hydrocarbons which comprise monoolefins containing one doublebond per molecule and polyolefins which contain more than one doublebond per molecule. Monoolefins which are utilized as unsaturated organiccompounds or olefin-acting compounds in the process of the presentinvention are either normally gaseous or normally liquid and includeethylene, propylene, l-butene, Z-butene, isobutylone, and highermolecular weight normally liquid olefins such as the various penteues,heirenes, heptenes, octenes, and still higher molecular weight liquidolefins, the latter including various olefin polymers having from about9 to about 18 carbon atoms per molecule including propylene trimer,propylene tctramer, propylene pentamer, etc. Cycloolcfins such ascyclopentene, methyl-cyclopentene, cyclohexene, methylcyclohexene, etc.,may also be utilizcd. Also included within the scope of the termunsaturated organic compound or olefin-acting compound are certainsubstances capable of producing olefinic hydrocarbons or intermediatesthereof under the conditions of operation utilized in the process.Typical olefin producing substances or olefin-acting compounds capableof use include alkyl halides capable of undergoing dehydrohalogenationto form olefinic hydrocarbons and thus containing at least two carbonatoms per molecule. Examples of such alkyl halides include ethylfluoride, n-propyl fluoride, isopropyl fluoride, n-butyl fluoride,isobutyl fluoride, sec-butyl fluoride, tert-butyl fluoride, etc., ethylchloride, n-propyl chloride, isopropyl chloride, n-butyl chloride,isobutyl chloride, sec-butyl chloride, tert-butyl chloride, etc., ethylbromide, n-propyl bromide, isopropyl bromide, n-butyl bromide, isobutylbromide, sec-butyl bromide, tert-butyl bromide, etc. As statedhereinabove, other esters such as alkyl sulfates including ethylsulfate, propyl sulfate, etc., and alkyl phosphates including ethylphosphate, etc. may be utilized. Ethers such as diethyl ether, ethylpropyl ether, dipropyl ether, etc., are also included within thegenerally broad scope of the term unsaturated organic compound orolefin-acting compound and may be successfully utilized as allrylatingagents in the process of this invention.

Olefin hydrocarbons, particularly normally gaseous olefin hydrocarbons,are preferred olefin-acting compounds or unsaturated organic compoundsfor use in the process of this invention and for passage by means ofline 1 to reaction zone a. The process of this invention can besuccessfully applied to and utilized for complete conversion of olefinhydrocarbons when these olefin hydrocarbons are present in minorquantities in various gas streams. Thus, in contrast to prior artprocesses, the normally gaseous olefin for use in the process of thisinvention need not be concentrated. Such normally gaseous olefinhydrocarbons appear in minor quantities in various refinery gas streams,usually diluted with various unreactive gases such as hydrogen,nitrogen, methane, ethane, propane, etc. These gas streams containingminor quantities of olefin hydrocarbons are obtained in petroleumrefineries from various refinery installations including thermalcracking units, catalytic cracking units, thermal re forming units,coking units, polymerization units, etc. Such refinery gas streams havein the past often been burned for fuel value since an economical processfor the utilization of their olefin hydrocarbon content has not beenavailable, or processes which have been taught by the prior art utilizesuch large quantities of alkylatable aromatic hydrocarbon that they havenot been economically feasible. This is particularly true for refinerygas streams known as off-gas streams containing relatively minorquantities or olefin hydrocarbons such as ethylene. Thus, it has beenpossible to catalytically polymerize propylene and/ or butenes invarious refinery gas streams, but the off-gases from such processesstill contain the utilizable olefin hydrocarbon, ethylene. Prior to myinvention, it has been considered necessary to concentrate this ethylenefor use as an alkylating agent. In addition to containing ethylene inminor quantities, these off-gas streams contain other olefinhydrocarbons, depending upon their source, including propylene andbutenes. A refinery ofi-gas ethylene stream may contain varyingquantities of hydrogen, nitrogen, methane, and ethane with the ethylenein minor proportion while a refinery elf-gas propylene stream isnormally diluted with propane and contains the propylene in minorquantities, and a refinery off-gas butene stream is normally dilutedwith butanes and contains the butenes in minor quantities. A typicalanalysis in mol percent for a utilizable refinery off-gas from acatalytic cracking unit is as follows: nitrogen, 4.0%; carbon monoxide,8.2%; hydrogen, 5.4%; methane, 37.8%; ethylene, 10.3%; ethane, 24.7%;propylene, 6.4%; propane, 10.7%; and C hydrocarbons, 0.5%. It is readilyobserved that the total olefin content of this gas stream is 16.7 molpercent and the ethylene content is even lower, namely 19.3 mol percent.Such gas streams containing olefin hydroca bons in minor or dilutequantities are particularly preferred unsaturated organic compounds orolefin-acting compounds within the broad scope of the invention. It isreadily apparent that only the olefin content of such streams undergoesreaction in the process of this invention, and that the remaining gasesfree from olefin hydrocarbons are vented from the process. It is one ofthe features of this invention that the non-reactive gases are ventedfrom the process with minimum loss of boron trifiuoride and alkylatablearomatic hydrocarbon due to their vapor pressure at the conditions oftemperature and pressure utilized for venting the non-reactive gases.

The unsaturated organic compound or olefin-acting compound or normallygaseous olefin hydrocarbon has combined therewith in line 1 alhylatablearomatic hydrocarbon from line 2 which may or may not have borontrifiuoride combined therewith from line 3 as will be set forth furtherin detail hereinafter. Many aromatichydrccarbons are utilizable asalkylatable aromatic hydrocarbons within the process of this invention.Preferred aromatic hydrocarbons are monocyclic aromatic hydrocarbons,that is, benzene hydrocarbons. Suitable aromatic hydrocarbons includebenzene, toluene, ortho- Xylene, meta-xylene, para-Xylene,ethyl-benzene, orthoethyltoluene, meta-ethyltoluene, para-ethyltoluene,1,2,3- trimethylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene,normal-propylbenzene, isopropylbenzene, normal-butylbenzene, etc. Highermolecular Weight alkylaromatic hydrocarbons are also suitable asstarting materials and include aromatic hydrocarbons such as areproduced by the prior alkylation of aromatic hydrocarbons with olefinpolymers. the art as alkylate, and include hexylbenzene, hexyltoluene,nonylbenzene, nonyltoluene, dodecylbenzene, dodecyltoluene, etc. Othersuitable alkylatable aromatic hydrocarbons include those with two ormore aryl groups such as diphenyl, diphenylmethane, triphenylmethane,

Such products are referred to in .acting compound, preferably olefin.

fiuorene, stilbene, etc. Examples of alkylatable aromatic hydrocarbonswithin the scope of this invention utilizable as starting materials andcontaining condensed benzene rings include naphthalene,alpha-methylnaphthalene, betamethylnaphthalene, etc., antbracene,phenanthrene, naphthacene, rubrene, etc. When the selected alkylatablearomatic hydrocrabon is a solid, it is heated by means not shown so thatit passes as a liquid through line 2 to line 1 as hereinabove described.Of the above alkylatable aromatic hydrocarbons for use as startingmaterials in the process of this invention, the benzene hydrocarbons arepreferred, and of the benzene hydrocarbons, benzene itself isparticularly preferred.

As stated hereinabove, when desired, boron trifluoride is admixed withthe alkylatable aromatic hydrocarbon prior to passage thereof to line 1.This is accomplished by passage of the boron triiluoride via line 3 toline 2. Boron trifiuoride is a gas, boiling point l01 C, melting point126 C., and is somewhat soluble in most organic solvents. It may be andgenerally is utilized per se by mere passage thereof as a gas throughline 3 under sufficient pressure so that it dissolves at least partiallyin the alkylatable aromatic hydrocarbon passing concurrently therewiththrough line 2. The boron trifiuoride may also be utilized as a solutionof the gas in an organic solvent. However, in the utilization of suchsolutions care must be exercised so that the selected solvent isunreactive with the unsaturated organic compound or olefinactingcompound or normally gaseous olefin hydrocarbon utilized in the process.Furthermore, boron trifiuoride complexes with many organic compounds,particularly those containing sulfur or oxygen atoms. Those complexeswhile utilizable as catalysts, are very stable and thus will interferewith the recovery of boron trifluoride in the ga s-liquid absorptionzone hereinafter set forth. Therefore, a further limitation upon theselection of such a solvent is that it be free from atoms or groupswhich form complexes with boron trifiuoride. Gaseous boron trifluorideitself is the preferred catalyst. The amount of boron trifiuoride whichis utilized is relatively small. It has been found that the amountnecessary can be conveniently expressed as grams of boron trifiuorideper gram mol of unsaturated organic compound or olefin- This amount ofboron trifiuoride will range from about 0.1 milligram to about 0.8 gramof boron trifluoride per gram mol of olefin utilized. When the amount ofboron trifluoride present in'the reaction zone is within the aboveexpressed range, substantially complete conversion of the olefinactingcompound is obtained, even when the olefin-acting compound is present inwhat might seem to be minor or dilute quantities in a gas stream.Furthermore, while theboron trifluoride as shown in the drawing isadded, when necessary, via linefi to line 2 it may, if desired, beadded, when necessary, directly to line 1, or to reaction zone 6.

Prior to entry from line 1 to reaction zone 6, the reactants andcatalyst, if any, have combined therewith recycle alkylatable aromatichydrocarbon via line 4, and polyalkylaromatic hydrocarbon absorber oilcontaining boron trifiuoride via line 5. Recycle alkylatable aromatichydrocarbon is generally available in the process since it is preferredto utilize a molar excess of alkylatable aromatic hydrocarbon overunsaturated organic compound, preferably olefin. This, as is disclosedin the prior art, has been found necessary to prevent side reactionsfrom taking place, such as polymerization of the unsaturated organiccompound prior to reaction thereof with the alkylatable aromatichydrocarbon, and to direct the reaction principally to monoalkylation.Polyalkylaromatic hydrocarbon produced in the process is recycled to thereaction zone via line 5 for three reasons. First of all, some transferof alkyl groups from polyalkylaromatic hydrocarbon to alkylatablearomatic hydrocarbon takes place in the reaction zone thus increasingthe yield per pass of desired alkylated aromatic hydrocarbon product;Second, the polyalkylaromatic hydrocarbon, as will be describedhereinafter, is a useful absorber oil to prevent loss of alkylatablearomatic hydrocarbon in the gas stream vented from the process. Third,and most important, since the polyalkylaromatic hydrocarbons arerelatively strongly basic, they dissolve boron trifluoride by complexformation from the effluent unreactive gases effectively and their usepermits a unitary combination process in which only minor quantites orno boron trifiuoride addition is necessary to maintain catalyst activityand desired reaction. The basic character of these polyalkylaromaticabsorber oils is pronounced in comparison to recycle of unalkylatedaromatic hydrocarbons or monoalkylated aromatic hydrocarbons.Furthermore, polyalkylaromatic hydrocarbons of certain structures aremuch more basic than other polyalkylaromatic hydrocarbons and it is apreferred embodiment of this invention to include such strongly basicpolyalkylaromatic hydrocarbons in the recycle stream for maximum borontrifluoride recovery and recycle. Such strongly basic polyalkylarornatichydrocarbons include those which have 1,3- dialkyl substitution,1,3,5-trialkyl substitution, and 1,2,4,5- tetralkyl substitution.Examples of such polyalkylaromatic hydrocarbons include1,3-diethylbenzene, 1,3,5-triethylbenzene, l,2,4,5-tetraethylbenzene andother polyalkylaromatic hydrocarbons in which the same structuralconfiguration is present. Therefore, the polyalkylaro matic hydrocarbonproduced in the process is first recycled to a gas-liquid absorptionzone for boron trifiuoride recovery, and is then recycled back to thereaction zone via line 5.

The combined feed to the reaction zone comprising alkylatable aromatichydrocarbon, unsaturated organic compound, boron trifluoride provided inthe manner hereinabove specified, and polyalkylaromatic hydrocarbon ispassed to reaction zone 6. Reaction zone 6 is of the conventional typeand may be equipped with heat transfer means, bafiles, trays, metalpacking, heating means, etc. The reaction zone preferably is of theadiabatic type and thus the feed to this zone will preferably beprovided with the requisite amount of heat proir to passage thereof tosaid zone. In a preferred embodiment, this reaction zone will beadiabatic and packed with a refractory oxide. The refractory oxide withwhich said zone is packed may be selected from among various inorganicoxides including alumina, silica, boria, or oxides of phosphorus (whichfor the purposes of this specification along with silica are consideredto be metal oxides), titanium dioxide, zirconium dioxide, chromia, zincoxide, magnesia, calcium oxide, silica-alumina, silica-magnesia,silica-aluminamagnesia, silica alumina zirconia, chromia-alumina,alumina-boria, silica-zirconia, etc., and various naturally occurringinorganic oxides of various states of purity such as bauxite, clay(which may or may not have been acid treated), diatomaceous earth, etc.Of the above mentioned inorganic oxides for use as packing in reactionzone 6, alumina is preferred.

The conditions utilized in reaction zone 6 may be varied over arelatively wide range. Thus, the desired alkylation reaction in thepresence of the above indicated boron trifiuoride catalyst may beeffected at a temperature of from about 0 F. or lower to about 500 F. orhigher, preferably at a temperature of from about F. to about 350 F. Thealkylation reaction is usually carried out at a pressure of from aboutsubstantially atmospheric to about 200 atmospheres. The pressureutilized is usually selected to maintain the alkylatable aromatichydrocarbon in substantially liquid phase. Within the above mentionedtemperature and pressure ranges, it is not always possible to maintainthe olefin-acting compound in liquid phase. Thus, when utilizing arefinery off-gas containing ethylene, the ethylene will be dissolved inthe liquid phase alkylatable aromatic hydrocarbon (and alkylatedaromatic hydrocarbon as formed) to the extent governed by temperature,pressure, and solubility considerations. However, a portion thereof willalways be in the gas phase. Referring to the aromatic hydrocarbon to bealkylated, it is preferable to have present from about 2 up to about ormore, sometimes up to 20, molar proportions per molar proportion ofolefin-acting compound introduced therewith. The hourly liquid spacevelocity of the liquid through the reaction zone may be varied over arelatively wide range of from about 0.25 to about 20 or more.

When the alkylation reaction has proceeded to the desired extent, theproducts from the alkylation zone, which may be termed alkylation zoneeifiuent, are withdrawn from zone 6 through line 7, are indirectly heatexchanged in heat exchanger 8 with recycle unreacted alkylatablearomatic hydrocarbon produced as hereinafter described, and are passedthrough line 9 to separator 10, also known as the alkylation reactionzone effluent received. The akylation or reaction zone effluout whichpasses into separation zone 1% comprises unreactive gases, if any, whichwere introduced to the system along with the unsaturated organiccompound, boron triiiuoride, excess allrylatable aromatic hydrocarbon,alkylated aromatic hydrocarbon, and polyalkylated aromatic hydrocarbon.The unreactive gases, if any, and the boron trifluoride are separated asgases in gasliquid separation zone 18, and passed through line 11 togas-liquid absorption zone 51, hereinafter described. Since thealkylatable aromatic hydrocarbon was utilized in excess in the reactionzone, the excess alkylatable aromatic hydrocarbon will be present inseparation zone 10 and a portion thereof will be vaporized overhead dueto its vapor pressure at these conditions alongwith-the unreactive gasesand boron trifiuorlde. The temperature of separation zone 19 will besomewhat less than that of the reaction zone, in most cases, due to thecooling which has taken place in heat exchanger 8 by indirect heatexchange with recycle alkylatable aromatic hydrocarbon. The liquid whichis separated in separation zone 10 passes therefrom through line 12 tothe first fractionation zone 13, labeled benzene column in the drawing.

Fractionation zone 13 is a conventional fractional distillation columnor tower and is utilized for the purpose of recovering excess unreactedalkylatable aromatic hydrocarbon for recycle from the reaction zoneeffluents. The recovered unreacted alkylatable aromatic hydrocarbonpasses overhead from first fractionation zone 13 through line 14containing condenser 15 to overhead receiver 16. A vent is placed onthis overhead receiver to remove any gases which have failed to beremoved by means of the gas-liquid absorption zone. This amount, ofcourse, is normally very small. These gases pass from overhead receiver16 through line 17 containing, if desired, a pressure control valve asshown. These gases may be passed, if desired, from line 17 back togas-liquid absorption zone 61, by means not shown, and if they are thusreturned to the gas-liquid absorption zone, this return will be to alower region thereof, as for example, by combination with and returnthrough line 11. The thus recovered unreacted alkylatable aromatichydrocarbon is withdrawn from overhead receiver 16 through line 18 bypump 19 which provides recycle to fractionation zone 13 by means oflines 20 and 21 and which also recycles the remainder of the recoveredalkylatable aromatic hydrocarbon via lines 26 and 4 back to line 1 andreaction zone 6. The higher boiling alkylated aromatic hydrocarbons arewithdrawn from fractionation zone 13 by means of line 22 and passedtherethrough to a second fractionation zone 25. A portion of the higherboiling alkyiated aromatic hydrocarbons is withdrawn from line 22 bymeans of line 23 containing reboiler 24 and passed back to a lowerregion of fractionation zone 13. By means of reboiler 24 the latedaromatic hydrocarbon.

10 requisite amount .of heat is furnished to fractionation zone 13.

Second fractionation zone 25 is of the conventional type and is utilizedfor recovery of desired alkylated aromatic hydrocarbon from higherboiling homologs thereof. The desired alkylated aromatic hydrocarbon iswithdrawn overhead from fractionation zone 25 through line 26 containingcondenser 27 and is passed to overhead receiver 28. The liquid productfrom overhead receiver 28 comprises desired alkylated aromatichydrocarbon which is withdrawn therefrom through line 29 by pump 30which provides reflux for fractionation zone 25 through lines 31 and 32.Pump 30 also provides a means for passage of desired alkylated aromatichydro carbon from the process by means of line 33. The still higherboiling alkylated aromatic hydrocarbons are withdrawn from fractionationzone 25 by means of line 34 and are passed to third fractionation zone3?. A portion of the higher boiling alkylated aromatic hydrocarbons arewithdrawn from line 34 through line 35 containing reboiler 36 and arepassed back to a lower region of fractionation zone 25. By means ofreboiler 36 the requisite amount of heat is supplied to thisfractionation zone.

As stated hereinabove, the higher boiling alkylated aromatichydrocarbons, in the preferred embodiment of this invention, arewithdrawn from fractionation zone 25 through line 34 and passed to athird fractionation zone 37. However, these higher boiling polyalkylatedaromatic hydrocarbons may be withdrawn from fractionation zone 25through line 34 and passed directly by means not shown through line 57to an upper region of gas-liquid absorption zone 61. This, of course, isa broad embodiment of the present invention and is utilized when norerunning of the higher boiling polyalkylated aromatic hydrocarbons isdesired and when the olefin-acting compound charged to the process asthe alkylating agent is a single compound such as ethylene instead of amixture of such compounds such as an ofigas containing both ethylene andpropylene. In the broad embodiment, when the polyalkylated aromatichydrocarbons are passed directly from the bottom of fractionation zone25 to an upper region of gas-liquid ab sorption zone 61, a quantitythereof may be withdrawn, if so desired, by means not shown, when thequantity of these higher boiling alkylated aromatic hydrocarbons is morethan is necessary for gas-liquid absorption zone 61.

Gas-liquid absorption zone 61 is a countercurrent contacting zone, ofconventional design, the size of which is varied depending upon thequantity of recycle higher boiling alkylated aromatic hydrocarbonspassed thereto and upon the quantity of unreacted alkylatable aromatichydrocarbon, boron trifluoride, and unreactive gases passed to a lowerregion thereof. In gas-liquid absorption zone 61 the higher boilingalkylated aromatic hydrocarbons pass into an upper region thereofthrough line 57 and flow downward in a countercurrent manner to thegases which are introduced thereto in a lower region thereof, forexample, via line 11. The unreacted alkylatable aromatic hydrocarbonvaporized in separation zone 10 and boron trifluoride are recovered,dissolved in and complexed with the higher boiling alky- The unreactivegases are vented from absorption zone 61 through line 62 containing apressure control valve as shown. The higher boiling alkylated aromatichydrocarbon containing d.ssolved unreacted alkylatable aromatichydrocarbon and boron trifluoride is withdrawn from the bottom ofgas-liquid absorption zone 61 through line 5 and recycled to re actionzone 6 as hereinabove set forth.

Depending upon whether or not the unsaturated organic compound utilizedin the process comprises one or more such compounds, and depending uponwhether or not rerunning of the higher boiling alkylated aro matichydrocarbons is deemed necessary or desirable, it

'unreactive gases. cumene are primary products of the process.

higher boiling alkylated aromatic hydrocarbons for use in the gas-liquidabsorption zone for recovery of gases hereinabove described. In thesimplest case, the unsaturated organic compound is an olefin such asethylene and the higher boiling alkylated aromatic hydrocarbon isrecycled to the gas-liquid absorption zone without rerunning. In thenext case, the unsaturated organic com- 1 pound is an olefin such asethylene and the higher boiling alkylated aromatic hydrocarbon is rerunto produce an overhead recycle fraction for the gas-liquid absorptionzone and to produce a bottoms fraction for removal from the process. Inanother case, and in a preferred embodiment of this invention, theunsaturated organic compound utilized is a mixture of normally gaseouolefins comprising both ethylene and propylene diluted with In such acase, both ethylbenzene and This is the typical case when the normallygaseous olefin hydrocarbon feed stream comprise a so-called refineryoffgas. In this case, the alkylated aromatic hydrocarbons higher boilingthan the first desired product are passed from fractionation zonethrough line 34 to a third fractionation zone 37.

Fractionation zone 37 is a conventional fractional distillation columnand is utilized, as set forth hereinabove. for either of two purposes.One purpose is to rerun higher boiling alkylated aromatic hydrocarbons.In this case, the higher boiling alkylated aromatic hydrocarbons arepassed overhead through line 38, condensed in condenser 39, and arepassed to overhead receiver 40. From overhead receiver 40 these higherboiling alkylated aromatic hydrocarbons are withdrawn through line 41 bypump 42 which provides reflux to the fractionation zone through lines 43and 44.- The higher boiling alkylated aromatic hydrocarbon for recyclepurposes is pumped from pump 42 through lines 43 and 44 to line 57 bymeans not shown. The bottoms from the process in this case are withdrawnthrough line 46. 'In the preferred embodiment, this fractionaldistillation column is utilized to remove overhead a second desiredalkylated aromatic hydrocarbon and to provide means for its recoveryfrom the process. This second desired alkylated aromatic hydrocarbonpasses overhead from fractionation zone 37 through line 38 containingcondenser 39 to overhead receiver 40. The liquid product from overheadreceiver 40 is withdrawn therefrom through line 41 by pump 42 which inthis embodiment also provides reflux to the fractionation zone throughlines 43 and 44. This pump also removes this second desired product fromthe process by passage thereof through line 45. The still higher boilingalkylated aromatic hydrocarbons are withdrawn from fractionation zone 37by means of line 46 and are passed to fourth fractionation zone 49. Aportion of -the higher boiling alkylated aromatic hydrocarbon iswithdrawn from line 46 through line 47 containing rcboiler 48 and ispassed back to a lower region of fractionation zone 37. By means ofreboiler 48, the requisite amount of heat is supplied to thisfractionation zone.

As stated hereinabove, the'higher boiling alkylated aromatichydrocarbons, in the preferred embodiment of this invention, arewithdrawn from fractionation zone 37 through line 46 and passed to afourth fractionation zone 49. However, these higher boilingpolyalkylated aromatic hydrocarbons may be withdrawn from fractionationzone 37 through line 46 and passed directly by means not shown throughline 57 to an upper region of gas-liquid absorption zone 61. Thisembodiment of the prment invention is utilized when no rerunning ofthese higher boiling polyalkylated aromatic hydrocarbons is desired andwhen the olefin-acting compound charged to the process is a mixture oftwo alkylating agents such as ethylene and propylene instead of beingsimply a single compound. In this embodiment when the polyalkylatedaromatic hydrocarbons are passed directly from the bottom offractionation zone 37 to an upper region of gas-liquid absorption zone61, a quantity thereof may be withdrawn through line 46, if so desired,by means not shown, when the quantity of these higher boiling alkylatedaromatic hydrocarbons is more than is necessary for gas-liquidabsorption zone 61.

In a further and preferred embodiment of this process wherein twoproducts are produced as hereinabove described and where it is desirableand/or advisable to fractionate the absorption zone recycle to removetar therefrom, a still further fourth fractionation zone can be utilizedas shown in the drawing. The second desired product from the process isremoved via lines 43 and as described hereinabove. The bottoms fromfractionation zone 37 are passed through line 46 to a recyclefractionation zone 49. Recycle fractionation zone 49 is a conventionalfractional distillation column by means of which polyalkylaromatichydrocarbon absorber oil is produced and by means of which tar isremoved from the process. The desired absorber oil, generallypolyalkylaromatic hydrocarbons, and more particularly those of thestructural configurations set forth hereinabove, is separated overheadfrom fractionation zone 49 through line 50 containing condenser 51 andpassed to overhead receiver 52. This liquid absorber oil is withdrawnfrom overhead receiver 52 through line 53 by means of pump 54 whichprovides recycle to this fractionation zone by means of lines 55 and 56.The net absorber oil separated overhead is also passed by pump 54through lines 55 and 57 to absorption zone 61. The tar and still higherboiling polyalkylaromatic hydrocarbons are removed from the process fromthe bottom of recycle zone 49 through line 58. A portion thereof iswithdrawn through line 59 containing reboiler 60 and is passed back to alower region of zone 49. Reboiler 60 provides the necessary amount ofheat for proper op eration of this fractionation zone.

The following example is introduced for the purposes of illustrationwith no intention of unduly limiting the generally broad scope of thisinvention. This example illustrates the utilization of the process ofthe present invention for the production of 500 barrels per day ofethylbenzene and 69 barrels per day of cumene. The catalyst utilizedcomprises about 0.5 gram of boron trifluoride per gram mol of olefin ina reaction zone packed with gamma-alumina. This example utilizes olfgasfrom a catalytic cracking unit containing both ethylene and propylene asalkylating agents for benzene. The production of the hereinabovedescribed quantities of ethylbenzene and cumene are hereinafter setforth with reference to the attached drawing.

Referring to the drawing, off-gas from a catalytic cracking unit in thequantity of 676 pound mols per hour, after compression, is fed to theplant through line 1. These 676 pound mols per hour are made up asfollows: 72 mols of hydrogen, 151 mols of nitrogen and carbon monoxide,281 mols of methane, 62.7 mols of ethylene, 96 mols of ethane; 9.3 molsof propylene, and 4 mols of propane. There is also charged to thereactor 71.3 pound mols 'per hour of fresh benzene through line 2 and0.05 pound mols per hour of makeup boron trifluoride through line 3.Also charged to the reactor are 558.5 pound mols per hour of recyclebenzene supplied through line 4. This 558.5 pound mols per hour of recycle benzene contains 0.055 mol of boron trifluoride,

0.7 mol of methane, 6.7 mols of ethane, 1.3 mols of propane, 549.0 molsof benzene, and 0.7 mol of ethylbenzene. By means of line 5 there isalso charged to the reactor through line 1 absorber rich recycle oilcontaining boron trifiuoride and condensed separator vapors, produced ashereinafter described, in the quantity of 412 pound mols per hour. This41.2 mols per hour is made of 0.412 mol of boron trifluoride, 0.3 mol ofmethane,

0.5 mol of ethane, 24.6 mols of benzene, 0.5 mol of ethylbenzene, 12.7mols. of diethyl benzene, and2.2 mols of ethylisopropylbenzene. Thecombined feed is passed from line 1 to reactor 6 in the quantity of1347.1 pound mols per hour. Reactor 6 is maintained at a pressure of 550p.s.i.g. and at a temperature of 250 F. The 1347.1 pound mols per hourof combined feed passing to reactor 6 contains 0.517 mol of borontrifluoride, 72.0 mols of hydrogen, 151.0 mols of nitrogen and carbonmonoxide, 282.0. mols of methane, 62.7 mols of ethylene, 103.2 mols ofethane, 9.3 mols of propylene, 5.3 mols of propane, 644.9 mols ofbenzene, 1.2 mols of ethylbenzene, 12.7 mols of diethylbenzene, and 2.2mols of ethylisopropylbenzene. The benzene to olefin ratio is 9-1 Inreactor 6 the olefin content of the off-gas stream reacts with thebenzene and alkyl groups are transferred from dialkylbenzene to benzeneto form monoalkylbenzene hydrocarbons. The reactor effluent passes fromreaction zone 6 through line 7, is heat exchanged with recycle benzene,as hereinafter described, in heat exchanger 8 and passes through line 9to gas-liquid separation zone 10. This reactor efiiuent in the quantityof 1275.0 pound mols per hour contains 0.513 mol of boron trifluoride,72.0 mols of hydrogen, 151.0 mols of nitrogen and carbon monoxide, 282.0mols of methane, no ethylene, 103.2 mols of ethane, no propylene, 5.3mols of propane, 576.2 mols of benzene, 60.9 mols of ethylbenzene, 7.3mols of cumene, 12.7 mols of diethylbenzene, 2.2 mols ofethylisopropylbenzene, 1.2 mols of diethylisopropylbenzene, 0.2 mol oftriethylisopropylbenzene, and 0.3

mol of diisopropylbenzene. In separator 10 the gaseous products from thereaction zone effluent are separated from the liquid products. Thegaseous products from the eilluent in the quantity of 618.2 pound molsper hour are passed from separator 10 to absorber 61, hereinafterdescribed. The liquid reactionzone efiiuent passesfrom separator 10through line 12 to fractionation zone 13, called the benzene column.

The benzene column 13 is fed with 656.8 pound mols per hour of separatorliquid. This 656.8 pound mols per hour contains 0.097 mol of borontrifluoride, 0.5' mol of hydrogen, 0.5 mol of nitrogen and carbonmonoxide, 5.0 mols of methane, 13.5 mols of ethane, 1.7 mols of propane,551.1 mols of benzene, 60.4 mols of ethylbenzene, 7.3 mols of cumene,12.7 molsof-diethylbenzene, 2.2 mols of ethylisopropylbenzene, 1.2 molsof diethylisopropylbenzene, 0.2 mol of triethylisopropylbenzene, and 0.3mol of diisopropylbenzene. In this benzene column 13 the benzene andlighter (or. lower boiling.

materials) are separated from the remaining liquid. Thus, there ispassed overhead from column 13 through 14 containing condenser 15 toreceiver 16 maintained at' 100 F., 573 pound mols per hour containing0.097 mol of boron trifluoride, 0.5 mol of hydrogen, 0.5 mol of nitrogenand carbon monoxide, 5.0 mols of methane, 13.5 mols of ethane, 1.7 molsof propane, 551.1 mols of benzene, and 0.7 mol of ethylbenzene. Fromreceiver 16 there is vented 14.5 pound mols per hour of gas through line17 containing a pressure control valve operating at 10 p.s.i.g. This14.5 pound mols contains 0.042 mol of boron trifluoride, 0.5 mol ofhydrogen, 0.5 mol of nitrogen and carbon monoxide, 4.3 mols of methane,6.8 mols of ethane, 0.4 mol of propane, and 2.0 mols of benzene. Thisvent gas is utilized for fuel or sent to a flare tower, or ashereinabove set forth may be recycled, by means not shown, to line 11and gas-liquid absorption zone 61.

The liquid in benzene column receiver 16 is withdrawn therefrom throughline 18 by pump 19.vvhichv discharges through line and supplies refluxto benzene column 13 by means of line 21. Net recycle benzene is pumpedby pump 19 through lines 20 and 4 back through heat exchange zone 8 toline 1 hereinabove described. The composition of this recyclebenzene..in

the quantity of '558.5-'pound mols per hour has been describedhereinabove. Aromatic hydrocarbons higher boiling than benzene arewithdrawn from the bottom of benzene column 13 through line 22 andpassed to ethylbenzene column 25. A portion thereof is passed via line23 through reboiler 24 to supply heat to the column.

Ethylbenzene column 25 is fed with 83.7 pound mols per hour of benzenecolumn bottoms contaning 59.7 mols of ethylbenzene, 7.3 mols of cumene,12.7 mols of diethylbenzene, 2.2 mols of ethylisopropylbenzene, 1.2 molsof diethylisopropylbenzene, 0.2 mol of triethylisopropylbenzene, and 0.3mol of diisopropylbenzene. This ethylbenzene column 25 separatesoverhead the net ethylbenzene produced. This ethylbenzene in thequantity of 59.7 pound mols per hour or 498 barrels per day passesthrough line 26, is condensed in condenser27 and passes to receiver 28.From receiver 28 this ethylbenzene is withdrawn through line 29 by pump30 which supplies reflux to column 25 through lines 31 and 32. The netethylbenzene passes through line 33 to storage. The bottoms fromethylbenzene column 25 pass through line 34 to cumene column 37. Aportion'thereof passes through line 35 and reboiler 36 to supply heat tothis ethylbenzene column.

Curnene column 37 is fed with 24 pound mols per hour from line 34. This24 pound mols per hour contains 7.3 mols of cumene, 12.7 mols ofdiethylbenzene, 2.2 mols of ethylisopropylbenzene, 1.2 mols ofdiethylisopropylbenzene, 0.2 mol of triethylisopropylbenzene, and 0.3mol of diisopropylbenzene. The function of this column is to separatethe cumene from the higher boiling liquids. Thus, 7.3 mols per hour ofcumene passes overhead from columnv 37 through line 38, is cooled incondenser 39 and passed to receiver 40. The liquid from receiver 40 iswithdrawn through line 41 by pump 42 which supplies reflux to column 37through lines 43 and 44. The net cumene is withdrawnthrough line 45 tostorage in the quantity of 69.3 barrels per day. The bottoms from cumenecolumn 37 are withdrawn therefrom through line 46 and passed to recyclecolumn 49. Cumene column 37 is heated by reboiling a portion of thesebottoms which pass through line 47 and reboiler 48 back to the column.

Recycle column 49'is fed with 16.7 pound'mols per hour ofpolyalkylaromatic hydrocarbons containing 12.7 mols of diethylbenzene,2.2 mols of ethylisopropylbenzene, 1.2 mos of diethylisopropylbenzene,0.2 mol of triethylisopropylbenzene, and 0.3 mol of diisopropylbenzene.The. purpose ofthis recycle column, in addition to removing tar asbottoms from the process, is to separate overhead polyalkylaromatichydrocarbons for use as absorber oil, and as a source of alkyl groupsfor alkyl transferreactions, as hereinbefore set forth. From recyclecolumn 49 there' is separated overhead 14.9 pound mols per hour ofpolyalkylaromatic hydrocarbons through line 50. These hydrocarbons arecondensed in condenser 51, and passed to overhead receiver 52. These14.9 pound mols per hour contain 12.7 mols of diethylbenzene and 2.2mols oiethylisopropylbenzene. The'liquid polyalkylaromatic hydrocarbonsare withdrawn from receiver 52 through line 53 by means of pump 54 whichsupplies reflux to column 49bymeans of lines 55 and 56. The bottoms'fromcolumn 49 in the quantity of 1.7 pound mols per hour-are withdravmtherefrom through line 58. A portion of these bottoms are circulatedthroughline 59 containing reboiler 69 for the purpose of supplying heatto the column. The 1.7 pound mols per hour containing 1.2 mols ofdiethylisopropylbenzene, 0.2 mol of triethylisopropylbenzene, and 0.3mol of diisopropylbeuzene are withdrawn as bottoms from the process.

The net liquid from receiver 52 in the quantity of 14.9 pound mols perhour as described hereinabove is pumped by pump 54 through lines 55 and57 to anupper region of absorption zone 61.. Absorption zone 61 is agas-liquid contacting zone for recovery of boron trifluoride and benzenefrom the separator gas. This separator gas in the quantity of 618.2pound mols per hour contains 0.416 mol of boron tn'fiuoride, 71.5mols'of hydrogen, 150.5 mols of nitrogen and carbon monoxide, 277.0 molsof methane, 89.7 mols of ethane, 3.6 mols of propane, 25.1 mols ofbenzene, and 0.5 mol of ethylbenzene. This separator gas enteringabsorption zone 61 through line 11 in a lower region of the absorptionzone is passed countercurrently to the 14.9 pound mols per hour ofpolyalkylaromatic hydrocarbon supplied through line 57. Recycle absorberoil passed from absorption zone 61 through lines 5 and 1 back toreaction zone 6. This rich absorption oil in the quantity of 40.8 molsper hour has been described hereinabove and contains 0.412 mol per hourof boron trifluoride which is greater than 99% of the boron trifluoridewhich separates as a gas overhead from separation zone 10. There isvented from absorption zone 61, 592 pound mols per hour of gas throughline 62. This absorption zone 61 operates at a temperature of 100 F. andis maintained at a pressure of 100 p.s.i.g. by means of a pressurecontrol valve in vent line 62. The 592. pound mols per hour of vent gasfrom line 62 contains 0.004 mol of boron trifluoride, 71.5 mols ofhydrogen, 150.5 mols of nitrogen and carbon monoxide, 276.7 mols ofmethane, 89.2 mols of ethane, 3.6 mols of propane, and 0.5 mol ofbenzene.

The mol balances in and out of the 500 barrel per day ethylbenzene plantare presented in the following table:

'16 boron trifluoride catalyst used in the reaction zone, or only 0.05mol per 67 .mols of combined ethylbenzene and cumene produced. V

I claim as my invention:

1. In the alkylation of an aromatic hydrocarbon in the presence of borontrifluoride in a reaction zone, the process which comprises separatingfrom the reaction zone eflrluent a gaseous fraction containing borontrifluoride, a liquid mono-alkylated aromatic hydrocarbon fraction and aliquid basic polyalkylated aromatic hydrocarbon fraction, scrubbing saidgaseous fraction with an absorber liquid consisting essentially of atleast a portion of said liquid polyalkylated aromatic fraction to absorbboron trifluoride in the last-named fraction, and supplying theresultant BF -containing polyalkylated aromatic hydrocarbon fraction tothe reaction zone.

2. The process of claim 1 further characterized in that said aromatichydrocarbon is a benzene hydrocarbon.

3. The process of claim 1 further characterized in that said aromatichydrocarbon is benzene which is alkylated with ethylene in said reactionzone.

4. The process of claim 1 further characterized in that said aromatichydrocarbon is benzene which is alkylated with propylene in saidreaction zone.

5. The process of claim 1 further characterized in that said aromatichydrocarbon is benzene which is alkylated with a butene in said reactionzone.

6. The process of claim 1 further characterized in that Table Mols/HourLean Gas Ofi Benzene BF; Ethyl- Cumene Bottoms Gas Benzene In Out 131%.-0.048 0. 004 0. 042 H, 72 71. 5 0. 5 151 150. 5 0. 5 CH4 281 276. 7 4.3C2H4- 62. 7 0 0 C2115. 96.0 89. 2 6. 8 C3Hu- 9. 3 0 0 03133. 4. O 3. 60. 4 0 H; 71. 3 0. 5 2. 0 CeHsC 59. 7 Ca 501 7- 7- 3 C5Ha(C25)r(CaH'/)- 1. 2 o 2(C2 a)s( a 1) 0.2 Ca KCaHfi' 0. 3

Alkyl Aromatic Yield (Molar):

On Benzene Percent Ethylb 83.9 94 1 Cumenn 10. 2} Bottoms-l-Loss- 5. 9

On Ethylene- Ethylb 95. 2 95. 2 Bofl'nm 4 8 Total 100. 0

On Propylene- Cumene. 78. 5 78. 5 Bnffnm 2L 5 Total 100. 0

From the table the following yield picture is observed: ethylbenzeneyield (molar) on benzeneis 83.9%. Cumene yield on benzene is 10.2%.Yield of monoalkylaromatic hydrocarbons is 94.1%. Benzene bottoms plusloss are 5.9%. Cumene yield based on propylene is 78.5%. Ethylbenzeneyield based on ethylene is 95.2%. Thus, high yields of alkyl aromaticsbased both on benzene and olefin charged to the process are obtained bythe process of the present invention. Furthermore, these yields. areattained with a net loss of about 1% of the said aromatic hydrocarbon istoluene which is alkylated with ethylene in said reaction zone.

7.v A process which comprises subjecting benzene to alkylation with agas containing ethylene and propylene in the presence of borontrifluoride in a reaction zone, separating from the reaction zoneefliuent a gaseous fraction containing boron trifinoride, anethylbenzene fraction, a cnmene fraction and a basic polyalkylbenzenefraction, scrubbing said gaseous fraction with an absorber liquidconsisting essentially of at least a portion of said poly- 17 18alkylbenzene fraction to absorb boron trifluoride in the 2,406,869 UphamSept. 3, 1946 last-named fraction, and supplying the resultantBFyCOntaining polyalkylbenzene fraction to the reaction zone. F PATENTS564,059 Great Bntam Sept. 12, 1944 References Cited in the file of thispatent 5 OTHER REFERENCES UNITED STATES PATENTS Thomas: AnhydrousAluminum Chloride in Organic 2,397,495 Lien et a1. Apr. 2, 1946Chemistry (1941), pp. 458-61 relied on.

1. IN THE ALKYLATION OF AN AROMATIC HYDROCARBON IN THE PRESENCE OF BORONTRIFLUORIDE IN A REACTION ZONE, THE PROCESS WHICH COMPRISES SEPARATINGFROM THE REACTION ZONE EFFLUENT A GASEOUS FRACTION CONTAINING BORONTRIFLUORIDE, A LIQUID MONO-ALKYLATED AROMATIC HYDROCARBON FRACTION AND ALIQUID BASIC POLYALKYLATED AROMATIC HYDROCARBON FRACTION, SCRUBBING SAIDGASEOUS FRACTION WITH AN ABSORBER LIQUID CONSISTING ESSENTIALLY OF ATLEAST A PORTION OF SAID LIQUID POLYALKYLATED AROMATIC FRACTION TO ABSORBBORON TRIFLUORIDE IN THE LAST-NAMED FRACTION, AND SUPPLYING THERESULTANT FB3-CONTAINING POLYALKYLATED AROMATIC HYDROCARBON FRACTION TOTHE REACTION ZONE.